Microphone



Sept 17, 1935 l G. R. EATON 2,014,427

MICROPHONE 4 Filed April 11, 1933 H Url-1E Patented Sept. 17, 1935 UNITED STATES MICROPHONE George R. Eaton, Oak Park, Ill., assignor to Kellogg Switchboard and Supply Company, Chicago, Ill., a corporation of Illinois Application April 11, 1933, Serial No. 665,538

Claims.

My invention relates to telephone instruments in which an electrical current is modified by passing thru a pair of electrodes separated by nely divided conducting material such as carbon or :5- some similar substance, the resistance of which is variable under the influence of one of the electrodes which is actuated by sound waves impinging thereon.' It relates more particularly to telephone transmitters for use in the hand set or French type telephone in which the receiver and transmitter are combined in a single instrument, though its usefulness is not limited to such a structure. 1

Due to the various positions in which a telephone instrument of this type is held While in use the type of transmitter used in the desk stand` telephone does not work satisfactorily therein. Transmitters comprising aback electrode having therein a substantially semispherical cavity within which a semispherically shaped front or movable electrode is positioned have proven particularly satisfactory in these instruments. In this type of transmitter the electrodes have therebetween a layer of granular conducting material in 25. such an amount as to insure contact between the J electrodes and the 'granular material at all times and in all positions in which the instrument may be placed.

An o bject of my invention is the provision oi a simple, easily manufactured and economical transmitter which is equally ecient in any position in which it may be placed while in use.

A feature of my invention is the elimination of a movable front contact mounted separately from the diaphragm.

One form of my invention resides in the provision of a movable electrode formed integral with the diaphragm of the transmitter. A

In the accompanying drawing, Fig. 1 shows a cross-sectionI of a preferred embodiment of the transmitter of my invention, and

Fig. 2 shows in detail a portion of the same. 'I'ne embodiment of my invention shown in the drawing comprises a cup-shaped supporting member 3 composed of suitable material and having a central opening 4 through which extends the portions 5 and 6 of afunnel shaped member Tof suitable conducting material which forms the back electrode of the transmitter. 'Ihe pori tion 8 also extends thru the central orifice shown in dotted lines in Fig. 2 of a member 8, where it is held by a screw 40 which passes thru the member 8 and engages the said portion 6. Screws Il extend thru bushings I I, insulating washers I 2 and I3 and a conducting plate II4 and engage tapped orices in the supporting member 3 to secure the members 8 and 4I in position relative thereto. The member 8 has a reduced portion 43 which passes thru a central orice in members 4I and II4 and prongs 42 are turned over the` 5 plate I I4 to secure the said members as a unit.

A diaphragm I4 has its periphery 9 associated with the inner peripheral edge I5 of the supporting member 3. A ring-shaped insulator I6 vfits between periphery 9 and a shoulder Il of mem- 10 ber 3 and a retaining disc I8 having a central opening engages the other side of periphery 9. A clamping ring I9 has screw threaded engagement with the member 3 and forces the disc I8, the' diaphragm I4 and insulator I6 against shoulder 15 Il and thereby clamps the edge 9 of diaphragm I4 against movement.

Radial fins or raised portions 2u are provided in the diaphragm I4 for strengthening the same and the central portion 2| is depressed to form a 20 semispherical portion. A shoulder 22 is formed between the depressed portion 2l and the dia-` phragm proper which engages a ring 23 formed of felt or some similar material which engages the end of the back electrode 1. 22 and radial fins 20 serve to innitely strengthen the diaphragm I4 and increase the emciency of the transmitter. The semispherical depression 2| enters a concave portion 24 formed in the back electrode I which may be concentric with the de- 30 pression 2 I. The back electrode 1depressed portion 2| and the ring 23 iorm a chamber into which granular carbon is placed in an amount suillcient to insure a good electrical contact between the electrodes at all times. The convex face of the 35' depressed portion 2| is supplied with a plating of gold or other like conducting metal to insure a good contact between the carbon granules and front electrode at all times. External electrical connections may be made to the conducting plate 40 II4 and member 3 which may be provided with terminals of anydesired type.

While I have shown and described a preferred embodiment of my invention I do not wishto be limited to the same but aim to cover all that which comes within the spirit andv scope of the vappended claims.

Having described my invention, what I claim as new and desire to secure by United States Letters Patent is:

1, In a microphone transmitter, a supporting member, a relatively stiff diaphragm, sufliciently thin to vibrate between its center and the supported periphery, a shoulder on said supporting member for receiving the periphery of said diaphragm,

The shoulder 25 a clamping member for securing said diaphragm on said shoulder, a light, thin, metallic, generally semispherical, hollow electrode fixed with said diaphragm substantially centrally thereof and extending laterally therefrom, said electrode having a surface of substantially unvarying conductivity, a fixed electrode mounted on said support, said fixed electrode having a generally semispherical microphone chamber therein, the electrode on said diaphragm being positioned substantially concentrically within said microphone chamber, the adjacent surfaces of said electrodes being spaced apart, granular microphonic material in the space between said electrodes and means for confining said microphonic material within said chamber.

2. In a microphone transmitter, a supporting member, a relatively stiff diaphragm, a shoulder on said supporting member for receiving the periphery of said diaphragm, a clamping member for securing said diaphragm on said shoulder,v

substantially the entire surface of said diaphragm Within its clamped periphery being exposed to the actuating voice currents, a light, thin, metallic, generally semispherical, hollow electrode fixed with said diaphragm substantially centrally thereof and extending laterally therefrom, a fixed electrode mounted on said support, said fixed electrode having a generally semspherical microphone chamber therein, the electrode on said diaphragm being positioned concentrically within said microphone chamber, the adjacent surfaces of said electrodes being spaced apart, granular microphonic material in the space between said electrodes and means for confining said microphonic material Within said chamber.

3. In a microphone transmitter, a supporting member, a relatively stiff, substantially flat circular diaphragm of sheet metal, sufficiently thin to vibrate between its center and the supported periphery, an annular shoulder on said supporting member for receiving, the periphery of said diaphragm, a clamping ring for securing said diaphragm on said shoulder, a light, thin metallic, generally semispherical, hollow electrode fixed with said diaphragm substantially centrally thereof and extending laterally therefrom, said electrode having a surface of unvarying conductivity, a fixed electrode mounted on said support, said fixed electrode having a generally semispherical microphone chamber therein, the electrode on said diaphragm being positioned substantially means for confining said microphonic material 5 within said chamber.

4. In a microphone transmitter, a supporting member, a relatively stiff, substantially flat circular diaphragm of sheet metal, sumciently thin to vibrate between its center and the supported pe- 1o riphery, an annular shoulder on said supporting member for receiving the periphery of said diaphragm, a clamping ring for securing said diaphragm on saidv shoulder, a light, thin metallic, .generally semispherical, l)hollow electrode fixed 15 with said diaphragm substantially centrallythereof and extending laterally therefrom, said electrode having a surface of unvarying conductivity, as by plating of a rare metal on its convex portion, `a fixed electrode mounted on said support, said 20 fixed electrode having a generally semispherical microphone chamber therein, the electrode on said diaphragm being positioned substantially concentrically within said microphone chamber, the adjacent surfaces of said electrodes being 25 spaced apart, granular microphonic material in the space between said electrodes and resilient means for confining said microphonic material within said chamber.

-5. In a microphone transmitter, a supporting 30 member, a relatively stiff diaphragm, a shoulder on said supporting member for receiving the periphery of said diaphragm, a clamping member for securing said diaphragm on said shoulder, substantially the entire' surface of said diaphragm 35 within its clamped periphery being exposed to the actuating voice currents, a light, thin, metallic, generally semispherical, hollow electrode fixed with saiddiaphragm substantially centrally thereof and extending laterally therefrom, a fixed 40 electrode mounted on said support, said fixed electrode having a microphone chamber therein, defined by atleast part of a generally semispherical surface, the electrode on said diaphragm being positioned concentrically within said microphone chamber, the adjacent surfaces of said electrodes being spaced apart, granular microphonic material inthe space between said electrodes and means for confining said microphonic material 50 within said chamber.

GEORGE R. EATON. 

